Canon MARK IV User Manual (en)

Troubleshooting Guide
If you operate the camera’s dial or lens during movie shooting, the 
respective operation noise will also be recorded. Using an external 
microphone (commercially available) is recommended (p.153).
If the LCD monitor is dirty, use a soft cloth to clean it.
In low or high temperatures, the LCD monitor display may seem slow 
or might look black. It will return to normal at room temperature.
The [4 Highlight alert] menu option is set to [Enable] (p.157).
The [4 AF point disp.] menu option is set to [Enable] (p.158).
If the image has been protected, it cannot be erased (p.172).
Set the color space to sRGB. If Adobe RGB is set, the first character 
will be an underscore (p.92).
With the [5 File name setting] menu option, select the camera’s 
unique file name or the file name registered under User setting 1 
When the movie is played, camera operation noise can be heard.
Display & Operation Problems
The LCD monitor does not display a clear image.
Part of the image blinks in black.
A red box is displayed on the image.
The image cannot be erased.
The file name’s first character is an underscore (“_”).
The fourth character in the file name changes.